When a blanket drum or an impression drum of a printer is cleaned, waste liquid is produced. A movement of applying some process to the waste liquid and disposing the processed waste liquid is promoted taking the terrestrial environment into consideration. In this instance, a cost (disposal cost) is required for the disposal process, and besides, since a large amount of cleaning liquid is used to clean a blanket drum and like elements, a high running cost is required.
Recently, it has been attempted to reprocess waste liquid to reuse cleaning liquid. One of the attempts is called settling method, and FIG. 30 shows a general configuration of a waste liquid regeneration apparatus used by the settling method. As shown in FIG. 30, the conventional waste liquid regeneration apparatus 51 includes a vessel 53 for storing cleaning waste liquid (waste liquid) 52. A bottom discharging pipe 54 is connected to the bottom wall of the vessel 53, and a side discharging pipe 55 is connected to a side wall of the vessel 53. Further, below an output of the bottom discharging pipe 54 from between the discharging pipes 54 and 55, a concentrated waste liquid recovery vessel 56 is disposed, and a regenerated cleaning liquid recovering vessel 57 is disposed below an exit of the side discharging pipe 55. Meanwhile, an on-off valve 58 is connected to a passage of the bottom discharging pipe 54, and another on-off valve 59 is connected on the upstream side to a passage of the side discharging pipe 55 and a filter 60 is connected on the downstream side with respect to the on-off valve 59.
In the waste liquid regeneration apparatus 51 having such a configuration as described above, waste liquid 52 after used to clean a blanket drum and other components of a printer is stored into the vessel 53 and some agent for promoting settling of ink pigment (sometimes referred to merely as pigment) 61 is added to the waste liquid 52 so that the ink pigment 61 is settled to the bottom of the vessel 53. Then, the settled ink pigment, that is, concentrated waste liquid 63, is recovered through the bottom discharging pipe 54 into the concentrated waste liquid recovery vessel 56, and supernatant liquid of the waste liquid 52 is filtered from the side discharging pipe 55 with the filter 60 to remove the ink pigment 61 and recovered into the regenerated cleaning liquid recovering vessel 57. cleaning liquid 62 obtained in this manner is reused.
With the method described, however, not only the purity of the regenerated cleaning liquid is insufficient, but depending upon the combination of the ink and the cleaning liquid, the settling of the ink pigment 61 is insufficient and the filter 60 suffers from clogging soon. Therefore, the method has a subject to be solved that exchange or cleaning of the filter 60 must be performed frequently.
Meanwhile, in the field of the electrophotograghy, also an aqueous development method wherein charged toner dispersed in solvent is deposited to an electrostatic latent image by electrophoresis so as to be visualized is adopted partially. Also a method for electrically removing charged toner powder from waste liquid after used for cleaning in the system just described has been proposed (official gazette of Japanese Patent Laid-Open NO. (Kokai) SHO53-10440). Further, a document (Kuroshima et al, A Collection of Japan Hardcopy '96 Theses, p153 (1996)) published recently in the society by the assignee of the present invention proposes a toner partie removing apparatus similar to an apparatus of the present invention.
However, the prior art of the official gazette and the technique of the document published in the society do not suppose a case wherein conductive water is mixed. For example, in the document published in the society, where water is contained in recovered carrier liquid, the difference in specific gravity between the carrier liquid and the water is utilized to separate the water. According to the method, however, not only a large-scale apparatus is required, but long time is inevitably required for the separation.
The present invention has been made in view of the subjects described above, and it is an object of the present invention to provide a waste liquid regeneration apparatus and a waste liquid regeneration method for a printer by which regeneration of cleaning liquid can be performed in a high efficiency to achieve reduction of the disposal cost for cleaning waste liquid and the running cost required for cleaning of the printer and besides improvement in productivity of the printer.